The inventor of the present invention previously designed a loudspeaker structure as indicated at 10 in FIG. 1 of the present application. The loudspeaker structure 10 includes a frame 11, a coil tube 12, and a magnetic element 13. The frame 11 has a top side formed with a concave resonant chamber 111 and a bottom side centrally provided with a through hole 112. A diaphragm 113 is fixedly attached to a periphery of the frame 11 and extends toward the resonant chamber 111. The coil tube 12 is a hollow tube. A coil unit 121 is fixedly mounted around the outer periphery of the coil tube 12 and has a first end whose outer periphery is fixed to the periphery of the through hole 112 such that a second end of the coil tube 12 is received in the resonant chamber 111 of the frame 11. The magnetic element 13 has a first end fixedly provided at a central position of the diaphragm 113 and a second end extending toward and received in the second end of the coil tube 12. The second end of the magnetic element 13 can move reciprocally along the axis of the coil tube 12.
When a current passes through and thus magnetizes the coil unit 121, an electromagnetic effect is produced between a central position of the resonant chamber 111 and the through hole 112, and magnetic lines generated by the coil unit 121 and magnetic lines generated by the magnetic element 13 create attractive and repulsive forces. As the audio signal current input to the coil unit 121 varies in magnitude and direction, the magnetic element 13 vibrates reciprocally along the axis of the coil tube 12 and thereby vibrates the air around the diaphragm 113, causing the loudspeaker structure 10 to make sound.
After the coil unit 121 is magnetized by the current, the highest density of the magnetic lines generated takes place at the two ends of the coil unit 121. However, as the second end of the magnetic element 13 is received in the second end of the coil tube 12 and adjacent to one end of the coil unit 121, the magnetic element 13 is subjected only to the magnetic force generated by one end of the coil unit 121 and cannot take full advantage of the dense magnetic lines at the other end of the coil unit 121. Therefore, the responsiveness of the magnetic element 13 to the magnetic attraction and repulsion caused by the coil unit 121 is low, and so is the output power of the loudspeaker structure 10. As a result, the sound reproduced by the loudspeaker structure 10 has a low acoustic volume and cannot be clearly heard.
To solve the aforesaid problems, it has been proposed to enlarge the magnetic element 13 so that the length of the magnetic element 13 matches the winding width of the coil unit 121, thus allowing the magnetic element 13 to be adjacent to both ends of the coil unit 121 while received in the coil tube 12 and take full advantage of the magnetic forces generated from both ends of the coil unit 121. However, this proposition will increase the weight of the magnet element 13 to such extent that, when the coil unit 121 is magnetized and applies attractive and repulsive forces to the magnetic element 13, the magnetic element 13 is slow in responding to such magnetic forces and tends to cancel the forces partially. In consequence, the magnetic element 13 fails to transmit its vibration sufficiently to the diaphragm 113, and the intensity of vibration of the diaphragm 113 is lowered, thereby preventing the loudspeaker structure 10 from reproducing a powerful sound.
Therefore, the issue to be addressed by the present invention is to design a novel loudspeaker and thereby overcome the various problems associated with the invention disclosed in FIG. 1. The present invention aims at providing a loudspeaker with a diaphragm equipped with a plurality of magnetic elements which have opposite magnetic orientations, are appropriately spaced apart, and are located in a coil tube at positions corresponding to relatively dense magnetic lines, thus widening the range in which the magnetic elements are distributed to be exposed to the magnetic forces generated by a coil unit, enhancing the attraction and repulsion of the magnetic elements, increasing the intensity of vibration of the diaphragm, and consequently raising the output power of the loudspeaker.